Initially κ -compact spaces for large κ

Stavros Christodoulou

Commentationes Mathematicae Universitatis Carolinae (1999)

  • Volume: 40, Issue: 2, page 319-325
  • ISSN: 0010-2628

Abstract

top
This work presents some cardinal inequalities in which appears the closed pseudo-character, ψ c , of a space. Using one of them — ψ c ( X ) 2 d ( X ) for T 2 spaces — we improve, from T 3 to T 2 spaces, the well-known result that initially κ -compact T 3 spaces are λ -bounded for all cardinals λ such that 2 λ κ . And then, using an idea of A. Dow, we prove that initially κ -compact T 2 spaces are in fact compact for κ = 2 F ( X ) , 2 s ( X ) , 2 t ( X ) , 2 χ ( X ) , 2 ψ c ( X ) or κ = max { τ + , τ < τ } , where τ > t ( p , X ) for all p X .

How to cite

top

Christodoulou, Stavros. "Initially $\kappa $-compact spaces for large $\kappa $." Commentationes Mathematicae Universitatis Carolinae 40.2 (1999): 319-325. <http://eudml.org/doc/248413>.

@article{Christodoulou1999,
abstract = {This work presents some cardinal inequalities in which appears the closed pseudo-character, $\psi _c$, of a space. Using one of them — $\psi _c(X) \le 2^\{d(X)\}$ for $T_2$ spaces — we improve, from $T_3$ to $T_2$ spaces, the well-known result that initially $\kappa $-compact $T_3$ spaces are $\lambda $-bounded for all cardinals $\lambda $ such that $2^\lambda \le \kappa $. And then, using an idea of A. Dow, we prove that initially $\kappa $-compact $T_2$ spaces are in fact compact for $\kappa = 2^\{F(X)\}$, $2^\{s(X)\}$, $2^\{t(X)\}$, $2^\{\chi (X)\}$, $2^\{\psi _c(X)\}$ or $\kappa = \max \lbrace \tau ^+, \tau ^\{<\tau \}\rbrace $, where $\tau > t(p,X)$ for all $p \in X$.},
author = {Christodoulou, Stavros},
journal = {Commentationes Mathematicae Universitatis Carolinae},
keywords = {initially $\kappa $-compact space; $\kappa $-bounded space; closed pseudocharacter; cardinal inequalities; initially -compact space; -bounded space; closed pseudocharacter for a space},
language = {eng},
number = {2},
pages = {319-325},
publisher = {Charles University in Prague, Faculty of Mathematics and Physics},
title = {Initially $\kappa $-compact spaces for large $\kappa $},
url = {http://eudml.org/doc/248413},
volume = {40},
year = {1999},
}

TY - JOUR
AU - Christodoulou, Stavros
TI - Initially $\kappa $-compact spaces for large $\kappa $
JO - Commentationes Mathematicae Universitatis Carolinae
PY - 1999
PB - Charles University in Prague, Faculty of Mathematics and Physics
VL - 40
IS - 2
SP - 319
EP - 325
AB - This work presents some cardinal inequalities in which appears the closed pseudo-character, $\psi _c$, of a space. Using one of them — $\psi _c(X) \le 2^{d(X)}$ for $T_2$ spaces — we improve, from $T_3$ to $T_2$ spaces, the well-known result that initially $\kappa $-compact $T_3$ spaces are $\lambda $-bounded for all cardinals $\lambda $ such that $2^\lambda \le \kappa $. And then, using an idea of A. Dow, we prove that initially $\kappa $-compact $T_2$ spaces are in fact compact for $\kappa = 2^{F(X)}$, $2^{s(X)}$, $2^{t(X)}$, $2^{\chi (X)}$, $2^{\psi _c(X)}$ or $\kappa = \max \lbrace \tau ^+, \tau ^{<\tau }\rbrace $, where $\tau > t(p,X)$ for all $p \in X$.
LA - eng
KW - initially $\kappa $-compact space; $\kappa $-bounded space; closed pseudocharacter; cardinal inequalities; initially -compact space; -bounded space; closed pseudocharacter for a space
UR - http://eudml.org/doc/248413
ER -

References

top
  1. Balogh Z., Dow A., Fremlin D.H., Nyikos P.J., Countable tightness and proper forcing, Bull. Amer. Math. Soc. 19 (1988), 295-298. (1988) Zbl0661.54007MR0940491
  2. Christodoulou S., Some topologies over a cardinal, Questions Answers Gen. Topology 10 (1992), 143-148. (1992) Zbl0782.54002MR1180472
  3. Dow A., On initially κ -compact spaces, in Rings of Continuous Functions; C. Aull ed., Lecture Notes in Pure and Applied Math. 95, 1985, pp.103-108. MR0789264
  4. Dow A., Compact spaces of countable tightness in the Cohen model, in Set Theory and Its Applications; LNM, 1401, 1989, pp.55-67. Zbl0684.54003MR1031765
  5. Hodel R., Cardinal functions I, in Handbook of Set-Theoretic Topology; K. Kunen and J.E. Vaughan eds., North-Holland, Amsterdam, 1984, pp.1-61. Zbl0559.54003MR0776620
  6. Juhasz J., Cardinal functions in topology - ten years later, Mathematical Centre Tracts 123, Mathematical Centrum - Amsterdam, 1980. Zbl0479.54001MR0576927
  7. Juhasz J., Cardinal functions II, in Handbook of Set-Theoretic Topology; K. Kunen and J.E. Vaughan eds., North-Holland, Amsterdam, 1984, pp.63-109. Zbl0559.54004MR0776621
  8. Koszmider P., Splitting ultrafilters of the thin-very tall algebra and initially ø m e g a 1 - compactness, preprint. 
  9. Stephenson R.M., Jr., Initially κ -compact and related spaces, in Handbook Set-Theoretic Topology; K. Kunen and J.E. Vaughan eds., North-Holland, Amsterdam, 1984, pp. 603-632. Zbl0588.54025MR0776632

NotesEmbed ?

top

You must be logged in to post comments.

To embed these notes on your page include the following JavaScript code on your page where you want the notes to appear.

Only the controls for the widget will be shown in your chosen language. Notes will be shown in their authored language.

Tells the widget how many notes to show per page. You can cycle through additional notes using the next and previous controls.

    
                

Note: Best practice suggests putting the JavaScript code just before the closing </body> tag.